The primary goals of this proposal are to quantify regional mu-opiate receptors and glucose metabolism in possible and probable Alzheimer's Disease and normal controls by positron emission tomography (PET) and to relate abnormalities of neuropsychological parameters in Alzheimer's Disease to PET findings. Additionally, we will determine the specificity of changes in mu-opiate receptors to Alzheimer's Disease by examining Multi Infarct Dementia patients in a similar manner. These results will 1) improve our understanding of the basic pathophysiology of Alzheimer's Disease, 2) relate parameters of cognitive decline to neurochemistry and 3) possible lead to earlier diagnosis of Alzheimer's Disease through quantification of mu-opiate receptors than possible by clinical examination or by measuring glucose metabolism.